Multilayer ceramic capacitor, multilayer ceramic capacitor series including the same, and multilayer ceramic capacitor mount body including the same

ABSTRACT

A body of a multilayer ceramic capacitor includes an inner layer portion and first and second outer layer portions sandwiching the inner layer portion therebetween. The inner layer portion includes an area extending from a conductive layer positioned closest to a first main surface to a conductive layer positioned closest to a second main surface in the stacking direction. The height of the body is smaller than the width of the body. The height of the inner layer portion is smaller than the width of the inner layer portion. The first outer layer portion includes a dielectric layer positioned closest to the first main surface. The second outer layer portion includes a dielectric layer positioned closest to the second main surface, and is thicker than the first outer layer portion. The total height of the first and second outer layer portions is smaller than the height of the inner layer portion.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a multilayer ceramic capacitor, amultilayer ceramic capacitor series including the same, and a multilayerceramic capacitor mount body including the same.

2. Description of the Related Art

An example of the related art that discloses a multilayer ceramiccapacitor in which the occurrence of cracks may be suppressed isJapanese Unexamined Patent Application Publication No. 2012-248581.

In the multilayer ceramic capacitor disclosed in this publication, abase unit includes an inner electrode body (inner layer portion) andfirst and second dielectric bodies (outer layer portions). The innerelectrode body includes first inner electrodes and second innerelectrodes facing each other with a dielectric member therebetween andstacked on each other. The first and second dielectric bodies sandwichthe inner electrode body therebetween in the stacking direction. Thefirst dielectric body including a first main surface of the base unit isthicker than the second dielectric body including a second main surfaceof the base unit in the stacking direction. One of the reasons whycracks occur is as follows. When a substrate having a multilayer ceramiccapacitor mounted thereon is deflected due to an external force, anexternal stress is produced. This external stress acts on a dielectriclayer of the multilayer ceramic capacitor, which causes the occurrenceof cracks. The present inventors have discovered another reason whycracks occur. When a multilayer ceramic capacitor is subjected tofiring, an internal stress is produced due to the difference in thecoefficient of thermal contraction between dielectric layers andconductive layers. This internal stress acts on the boundary between theinner layer portion and the outer layer portion, thus causing theoccurrence of cracks (delamination). The present inventors have alsodiscovered that this type of crack is more likely to occur when theinner layer portion is made thick by increasing the number of layers tobe stacked in order to increase the electrostatic capacitance of themultilayer ceramic capacitor.

In the multilayer ceramic capacitor disclosed in the above-describedpublication, the occurrence of cracks caused by an external stress maybe suppressed, but the occurrence of cracks caused by an internal stressproduced by the difference in the coefficient of thermal contractionbetween dielectric layers and conductive layers is not considered.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention have been conceived anddeveloped in view of the above-described problem. Preferred embodimentsof the present invention provide a multilayer ceramic capacitor in whichit is possible to significantly reduce or prevent the occurrence ofcracks caused by an internal stress produced by the difference in thecoefficient of thermal contraction between dielectric layers andconductive layers while securing a sufficient electrostatic capacitance.

According to a preferred embodiment of the present invention, amultilayer ceramic capacitor includes a body and at least two outerelectrodes. The body includes a plurality of dielectric layers and aplurality of conductive layers stacked on each other and includes firstand second main surfaces opposing each other in a stacking direction.The outer electrodes are disposed on at least some surfaces of the bodyand are electrically connected to at least some of the plurality ofconductive layers. The body includes first and second end surfaces whichoppose each other so as to connect the first and second main surfacesand first and second side surfaces which oppose each other so as toconnect the first and second main surfaces and also to connect the firstand second end surfaces. The body includes an inner layer portion andfirst and second outer layer portions which sandwich the inner layerportion therebetween. The inner layer portion includes an area extendingfrom a conductive layer positioned closest to the first main surfaceamong the plurality of conductive layers to a conductive layerpositioned closest to the second main surface among the plurality ofconductive layers in the stacking direction. The height of the body inthe stacking direction is smaller than the width of the body in adirection in which the first and second side surfaces are connected toeach other with a shortest distance. The height of the inner layerportion in the stacking direction is smaller than the width of an areaof the inner layer portion where the plurality of conductive layers arestacked in a direction in which the first and second side surfaces areconnected to each other with a shortest distance. The height of thesecond outer layer portion is greater than that of the first outer layerportion. The total height of the first outer layer portion and thesecond outer layer portion is smaller than the height of the inner layerportion in the stacking direction.

The width of the body may be greater than about 0.9 mm and the height ofthe body may be smaller than about 0.9 mm, for example.

The height of the second outer layer portion may be about 90 μm orgreater and may be equal to or smaller than about ¼ of the height of theinner layer portion, for example.

The second outer layer portion may include an outer portion includingthe second main surface and an inner portion disposed between the outerportion and the inner layer portion. The composition ratio of Si to Tiof a dielectric layer included in the outer portion may be higher thanthat of dielectric layers, which are some of the plurality of dielectriclayers, included in the inner layer portion and a dielectric layerincluded in the inner portion.

The height of the outer portion may be equal to or greater than that ofthe inner portion in the stacking direction.

The outer portion may include a boundary region adjacent to the innerportion which has a larger Si content compared to a central region ofthe inner portion.

The difference between the height of the second outer layer portion andthat of the first outer layer portion may be about 10 μm or greater, forexample.

As viewed from a direction in which the first and second side surfacesare connected to each other, the boundary region may include a portionwhich inclines toward the center of the body in the width direction asthe boundary region is positioned closer to the first and second endsurfaces.

The composition ratio of a rare earth element to Ti of the dielectriclayer included in the outer portion may be higher than that of thedielectric layer included in the inner portion.

The composition ratio of Dy to Ti of the dielectric layer included inthe outer portion may be higher than that of the dielectric layerincluded in the inner portion.

The composition ratio of Mn to Ti of the dielectric layer included inthe outer portion may be higher than that of the dielectric layerincluded in the first outer layer portion.

According to another preferred embodiment of the present invention, amultilayer ceramic capacitor series includes a plurality of theabove-described multilayer ceramic capacitors and a package including anelongated carrier tape and a cover tape. The elongated carrier tapeincludes a plurality of cavities disposed apart from each other in whichthe plurality of multilayer ceramic capacitors are stored. The covertape is attached to the elongated carrier tape so as to cover theplurality of cavities. The plurality of multilayer ceramic capacitorsare stored in the plurality of respective cavities such that the secondmain surfaces of the plurality of multilayer ceramic capacitors facebottom sides of the plurality of respective cavities.

According to another preferred embodiment of the present invention, amultilayer ceramic capacitor mount body includes the above-describedmultilayer ceramic capacitor and a substrate on which the multilayerceramic capacitor is mounted. The multilayer ceramic capacitor ismounted on the substrate with the second main surface facing thesubstrate.

The substrate may include a pair of lands on a surface of the substrate.The pair of lands may be electrically connected to a pair of outerelectrodes of the multilayer ceramic capacitor. In the width directionof the body, the width of the pair of lands is smaller than the width ofthe body.

In the width direction of the body, the width of the pair of lands maybe smaller than the width of the inner layer portion.

According to preferred embodiments of the present invention, in amultilayer ceramic capacitor, it is possible to significantly reduce orprevent the occurrence of cracks caused by an internal stress producedby the difference in the coefficient of thermal contraction betweendielectric layers and conductive layers while securing a sufficientelectrostatic capacitance.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of a multilayer ceramic capacitoraccording to a first preferred embodiment of the present invention.

FIGS. 2 and 3 are sectional views taken along lines II-II and III-III,respectively, of FIG. 1.

FIGS. 4 and 5 are sectional views taken along lines IV-IV and V-V,respectively, of FIG. 2.

FIG. 6 is a flowchart illustrating a manufacturing method for amultilayer ceramic capacitor according to the first preferred embodimentof the present invention.

FIG. 7 is a sectional view illustrating the configuration of amultilayer ceramic capacitor mount body according to the first preferredembodiment of the present invention.

FIG. 8 is a plan view illustrating the configuration of a multilayerceramic capacitor series according to the first preferred embodiment ofthe present invention.

FIG. 9 is a sectional view taken along line IX-IX of FIG. 8.

FIG. 10 is an external perspective view of a multilayer ceramiccapacitor according to a second preferred embodiment of the presentinvention.

FIGS. 11 and 12 are sectional views taken along lines XI-XI and XII-XII,respectively, of FIG. 10.

FIGS. 13 and 14 are sectional views taken along lines XIII-XIII andXIV-XIV, respectively, of FIG. 11.

FIG. 15 is a flowchart illustrating a manufacturing method for amultilayer ceramic capacitor according to the second preferredembodiment of the present invention.

FIG. 16 is an exploded perspective view illustrating the multilayerstructure of a set of unit sheets defining a partial body of amultilayer ceramic capacitor of the second preferred embodiment withoutan outer portion.

FIG. 17 is a sectional view illustrating a state in which a set ofmother sheets are being pressure-bonded.

FIG. 18 is a sectional view illustrating a state in which a set ofpressure-bonded mother sheets and a plurality of second ceramic greensheets are being pressure-bonded.

FIG. 19 is a sectional view illustrating the configuration of amultilayer ceramic capacitor mount body according to the secondpreferred embodiment of the present invention.

FIG. 20 is a sectional view illustrating a state in which a set ofmother sheets defining a multilayer ceramic capacitor according to athird preferred embodiment of the present invention are beingpressure-bonded.

FIG. 21 is a sectional view illustrating a state in which a set ofpressure-bonded mother sheets and a plurality of second ceramic greensheets are being pressure-bonded.

FIG. 22 is a sectional view illustrating a state in which a mother bodyis divided.

FIG. 23 illustrates an example of an enlarged image of a cross sectionof a multilayer ceramic capacitor observed with a scanning electronmicroscope (SEM).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will be given below, with reference to the accompanyingdrawings, of a multilayer ceramic capacitor, a multilayer ceramiccapacitor series including the same, and a multilayer ceramic capacitormount body including the same according to preferred embodiments of thepresent invention. In the following description of the preferredembodiments, the same element or corresponding elements shown in thedrawings are designated by like reference numeral, and an explanationthereof will be given only once. The multilayer ceramic capacitor willbe simply referred to as a “capacitor”.

First Preferred Embodiment

FIG. 1 is an external perspective view of a capacitor according to afirst preferred embodiment of the present invention. FIGS. 2 and 3 aresectional views taken along lines II-II and III-III, respectively, ofFIG. 1. FIGS. 4 and 5 are sectional views taken along lines IV-IV andV-V, respectively, of FIG. 2. In FIGS. 1 through 5, the length directionof a body 11, which will be discussed below, is indicated by L, thewidth direction thereof is indicated by W, and the height directionthereof is indicated by T.

As shown in FIGS. 1 through 5, the capacitor 10 includes the body 11 andtwo outer electrodes 14. The body 11 includes a plurality of dielectriclayers 12 and a plurality of conductive layers 13 stacked on each other,and has first and second main surfaces 111 and 112 opposing each otherin the stacking direction. The two outer electrodes 14 are disposed onsome surfaces of the body 11 and are electrically connected to some ofthe plurality of conductive layers 13.

The stacking direction of the dielectric layers 12 and the conductivelayers 13 is perpendicular to the length direction L and the widthdirection W of the body 11. That is, the stacking direction of thedielectric layers 12 and the conductive layers 13 is parallel with theheight direction T of the body 11.

The body 11 includes first and second end surfaces 113 and 114. Thefirst and second end surfaces 113 and 114 oppose each other so as toconnect the first and second main surfaces 111 and 112. The body 11 alsoincludes first and second side surfaces 115 and 116. The first andsecond side surfaces 115 and 116 oppose each other so as to connect thefirst and second main surfaces 111 and 112 also to connect the first andsecond end surfaces 113 and 114. The body 11 preferably has arectangular or substantially rectangular parallelepiped shape, and mayhave a rounded portion at least in one of a corner and a ridge of thebody 11.

The shortest distance between the first and second side surfaces 115 and116 is smaller than that between the first and second end surfaces 113and 114. That is, the width W₀ of the body 11 in the width direction Wis smaller than the length L₀ of the body 11 in the length direction L.The height T₀ of the body 11 in the stacking direction is smaller thanthe width W₀ of the body 11 in a direction in which the first and secondside surfaces 115 and 116 are connected to each other with the shortestdistance. The height T₀ of the body 11 is preferably greater than about⅓ of the length L₀ of the body 11 and smaller than about ½ of the lengthL₀ of the body 11, for example, which will be discussed later. Theheight T₀ of the body 11 is preferably smaller than the width W₁ of aninner layer portion 11 m, which will be discussed later. The width W₀ ofthe body 11 is preferably greater than about 0.9 mm, and the height T₀of the body 11 is preferably smaller than about 0.9 mm, for example.

The body 11 includes an inner layer portion 11 m and first and secondouter layer portions 12 b ₁ and 12 b ₂ which sandwich the inner layerportion 11 m therebetween. The inner layer portion 11 m includes an areaextending from a conductive layer 13 positioned closest to the firstmain surface 111 among the plurality of conductive layers 13 to aconductive layer 13 positioned closest to the second main surface 112among the plurality of conductive layers 13 in the stacking direction ofthe body 11.

The first outer layer portion 12 b ₁ includes a dielectric layer 12positioned closest to the first main surface 111 among the plurality ofdielectric layers 12. The second outer layer portion 12 b ₂ includes adielectric layer 12 positioned closest to the second main surface 112among the plurality of dielectric layers 12.

In the inner layer portion 11 m, at least some of the plurality ofdielectric layers 12 and the plurality of conductive layers 13 arealternately stacked on each other. That is, the inner layer portion 11 mincludes all the conductive layers 13. All the conductive layers 13preferably are rectangular or substantially rectangular, as viewed fromabove, as shown in FIGS. 4 and 5.

In the first preferred embodiment, all the conductive layers 13preferably are electrically connected to either one of the two outerelectrodes 14. Alternatively, at least some of the conductive layers 13may be electrically connected to one of the outer electrodes 14. Thatis, among the plurality of conductive layers 13, there may be someconductive layers 13 that are not electrically connected to any outerelectrodes 14.

The two outer electrodes 14 are disposed at both ends of the body 11 inthe length direction L. More specifically, one of the two outerelectrodes 14 is disposed at one end of the body 11 close to the firstend surface 113 in the length direction L, while the other one of thetwo outer electrodes 14 is disposed at the other end of the body 11close to the second end surface 114 in the length direction L. In thefirst preferred embodiment, one of the two outer electrodes 14 extendsfrom the first end surface 113 continuously to the first and second mainsurfaces 111 and 112 and to the first and second side surfaces 115 and116. The other one of the two outer electrodes 14 extends from thesecond end surface 114 continuously to the first and second mainsurfaces 111 and 112 and to the first and second side surfaces 115 and116. However, the arrangement of the two outer electrodes 14 is notrestricted to that described above. The two outer electrodes 14 may bedisposed on some surfaces of the body 11 to be electrically connected tothe plurality of conductive layers 13 and so that the capacitor 10 canbe mounted.

One of the two outer electrodes 14 is connected to some of the pluralityof conductive layers 13 on the first end surface 113, while the otherone of the two outer electrodes 14 is connected to the remainingconductive layers 13 on the second end surface 114. The conductivelayers 13 connected to the first end surface 113 and the remainingconductive layers 13 connected to the second end surface 114 arealternately stacked on each other such that they face each other with afirst dielectric layer 12 therebetween in the inner layer portion 11 m.

As shown in FIG. 3, the height T₁ of the inner layer portion 11 m in thestacking direction of the body 11 is smaller than the width W₁ of theinner layer portion 11 m where the plurality of conductive layers 13 arepositioned, in the width direction W of the body 11 in which the firstand second side surfaces 115 and 116 are connected to each other withthe shortest distance.

The second outer layer portion 12 b ₂ is thicker than the first outerlayer portion 12 b ₁. That is, the height h₂ of the second outer layerportion 12 b ₂ is greater than the height h₁ of the first outer layerportion 12 b ₁. The total height of the height h₁ of the first outerlayer portion 12 b ₁ and the height h₂ of the second outer layer portion12 b ₂ is smaller than the height T₁ of the inner layer portion 11 m.The difference between the height h₂ of the second outer layer portion12 b ₂ and the height h₁ of the first outer layer portion 12 b ₁ ispreferably equal to or greater than about 10 μm, for example. It ispreferable that the height h₂ of the second outer layer portion 12 b ₂be equal to or greater than about 90 μm and be equal to or smaller thanabout ¼ of the height T₁ of the inner layer portion 11 m, for example.

The height T₀ of the body 11 in the stacking direction of the body 11 isequal to the total height of the height T₁ of the inner layer portion 11m, the height h₁ of the first outer layer portion 12 b ₁, and the heighth₂ of the second outer layer portion 12 b ₂.

It is preferable that, in the width direction W of the body 11, themaximum width of side gaps 12 c provided between each of the first andsecond side surfaces 115 and 116 and the inner layer portion 11 m begreater than the height h₁ of the first outer layer portion 12 b ₁. Itis also preferable that the average width ((W₀−W₁)/2) of the side gaps12 c be greater than the height h₁ of the first outer layer portion 12 b₁. It is more preferable that the maximum width or the average width((W₀−W₁)/2) of the side gaps 12 c be greater than about 30 μm andsmaller than about 90 μm, for example. The maximum width and the averagewidth ((W₀−W₁)/2) of the side gaps 12 c will be discussed later.

The configuration of each of the elements defining the capacitor 10 willbe described in detail.

The plurality of dielectric layers 12 each preferably contain aperovskite compound expressed by ABO₃ (“A” contains Ba, and “B” containsTi, and O is oxygen) as a principal component. That is, the plurality ofdielectric layers 12 each contain barium titanate (BaTiO₃) as aprincipal component.

The plurality of dielectric layers 12 each contain Si as a secondarycomponent. Si is contained in the dielectric layers 12 by adding a Sicompound, such as glass or SiO₂, as a secondary component to aperovskite compound expressed by ABO₃ as a principal component. Anothercompound, such as a Mn compound, an Mg compound, a Co compound, a Nicompound, or a rare earth compound, may be added to a perovskitecompound expressed by ABO₃.

As a material for each of the plurality of conductive layers 13, ametal, such as Ni, Cu, Ag, Pd, or Au, or an alloy containing at leastone of such metals (for example, an alloy of Ag and Pd) may be used. Thethickness of each conductive layer 13 after a firing step is preferablyabout 0.4 to 0.9 μm, for example. If the thickness of each of theconductive layers 13 is smaller than about 0.4 μm, it is difficult tosecure the coverage of the conductive layers 13. If the thickness ofeach of the conductive layers 13 is greater than about 0.9 μm, it isdifficult to secure the electrostatic capacitance per unit volume of thecapacitor 10.

The two outer electrodes 14 each include a foundation layer which coversboth end portions of the body 11 and a plated layer which covers thisfoundation layer. As a material for the foundation layer, a metal, suchas Ni, Cu, Ag, Pd, or Au, or an alloy containing at least one of suchmetals (for example, an alloy of Ag and Pd) may be used. The thicknessof the foundation layer is preferably about 10.0 to 50.0 μm, forexample.

The foundation layer may be formed by baking a conductive paste appliedto both end portions of the body 11 which has been fired. Alternatively,the foundation layer may be formed by firing, together with theconductive layers 13, a conductive paste applied to both end portions ofthe body 11 which has not been fired. Alternatively, the foundationlayer may be formed by plating both end portions of the body 11 or bycuring a conductive resin containing thermosetting resin applied to bothend portions of the body 11.

If the foundation layer is made of a conductive resin, it is possible toreduce a load imposed on the body 11 caused by an external stress whichis produced when a substrate having the capacitor 10 mounted thereon isdeflected due to an external force and thus to significantly reduce orprevent the occurrence of cracks in the body 11. Accordingly, by formingthe second outer layer portion 12 b ₂ thick and then by forming the twoouter electrodes 14 having a conductive resin, the occurrence of cracksin the body 11 can further be significantly reduced or prevented.

As a material for the plated layer, a metal, such as Sn, Ni, Cu, Ag, Pd,or Au, or an alloy containing at least one of such metals (for example,an alloy of Ag and Pd) may be used.

The plated layer may be constituted by a plurality of layers. In thiscase, the plated layer is preferably a two-layer structure in which a Snplated layer is formed on a Ni plated layer. In this case, the Ni platedlayer functions as a solder barrier layer, while the Sn plated layerimproves solder wettability. The thickness of one plated layer ispreferably about 1.0 to 10.0 μm.

A manufacturing method for the capacitor 10 according to the firstpreferred embodiment of the present invention will be described belowwith reference to the flowchart of FIG. 6. In this manufacturing method,a plurality of capacitors 10 are mass-produced at one time together inthe following manner. Elements which will form a plurality of capacitors10 are processed together until a halfway point through a manufacturingprocess so as to fabricate a mother body. Then, the mother body isdivided into individual flexible bodies. The individual flexible bodiesare then processed, thus manufacturing a plurality of capacitors 10.

In step S11, ceramic slurry is prepared first. More specifically, aceramic powder, a binder, and a solvent are mixed at a predeterminedmixing ratio so as to form the ceramic slurry.

Then, in step S12, ceramic green sheets are formed. More specifically,the ceramic slurry is formed into a sheet shape on a carrier film byusing a die coater, a gravure coater, or a micro gravure coater, thusforming the ceramic green sheets.

Then, in step S13, mother sheets are formed. More specifically, aconductive paste is printed on each ceramic green sheet by using screenprinting or gravure printing such that a predetermined conductivepattern is formed on the ceramic green sheet. As a result, a mothersheet, which is a ceramic green sheet having a predetermined conductivepattern thereon, is formed.

Then, in step S14, the mother sheets are stacked. By stacking theplurality of mother sheets according to a predetermined rule, a set ofmother sheets is formed. In the first preferred embodiment, a pluralityof mother sheets forming the first outer layer portion 12 b ₁, aplurality of mother sheets forming the inner layer portion 11 m, and aplurality of mother sheets forming the second outer layer portion 12 b ₂are stacked on each other in this order, thus forming a set of mothersheets.

Then, in step S15, the set of mother sheets is pressure-bonded. A flatdie, which is not shown, is pressed against the mother sheets formingthe second outer layer portion 12 b ₂ along the stacking direction, thuspressure-bonding the set of mother sheets placed on a base, which is notshown. As a result, a mother body is fabricated.

Then, in step S16, the mother body is divided. More specifically, themother body is press-cut or cut with a dicing machine in a matrix intoflexible bodies.

Then, in step S17, the flexible bodies are fired. More specifically, theflexible bodies are heated to a predetermined temperature so as to firethe ceramic dielectric material and the conductive material. The firingtemperature is set suitably in accordance with the type of ceramicdielectric material and the type of conductive material, and may be setwithin a range of about 900 to 1300° C.

Then, in step S18, the flexible bodies are barrel-polished. Morespecifically, the flexible bodies subjected to firing are sealed withina small box called a barrel, together with media balls having a higherhardness than the ceramic material. Then, by rotating the barrel, theflexible bodies are polished. By performing this barrel-polishing, theouter surfaces (in particular, corners and ridges) of the flexiblebodies are curved and rounded. As a result, the body 11 is formed.

Then, in step S19, outer electrodes are formed. More specifically, aconductive paste is applied to an end portion including the first endsurface 113 and an end portion including the second end surface 114 ofthe body 11 so as to form a metal film, and then, the metal film isfired. Then, the metal film is sequentially Ni-plated and Sn-plated. Asa result, the two outer electrodes 14 are formed on the outer surfacesof the body 11.

Through the above-described series of steps, the capacitor 10 configuredas shown in FIGS. 1 through 5 is manufactured.

In the capacitor 10 of the first preferred embodiment, the height T₀ ofthe body 11 is smaller than the width W₀ of the body 11, and the heightT₁ of the inner layer portion 11 m is smaller than the width W₁ of theinner layer portion 11 m. That is, by increasing the width of theconductive layers 13 while maintaining the size of the side gaps 12 cwithout increasing the number of layers within the inner layer portion11 m, a sufficient electrostatic capacitance of the capacitor 10 issecured. Since the height T₀ of the body 11 is smaller than the width W₀of the body 11, the main surfaces 111 and 112 and the side surfaces 115and 116 can be distinguished from each other from the outerconfiguration of the body 11.

It is now assumed that, for securing a sufficient electrostaticcapacitance, the height T₁ of the inner layer portion 11 m is increasedby increasing the number of layers within the inner layer portion 11 m.In this case, the internal stress produced by the difference in thecoefficient of thermal contraction between the dielectric layers 12 andthe conductive layers 13 during the firing step for the capacitor 10 isincreased. Additionally, when pressure-bonding a set of mother sheets,the pressure is less likely to be applied to the plurality of dielectriclayers 12 positioned in the side gaps 12 c, thus decreasing theadherence between the dielectric layers 12 in the side gaps 12 c. As aresult, it is more likely that cracks (delamination) will occur at theboundary between the inner layer portion 11 m and the second outer layerportion 12 b ₂.

Even if the width W₁ of the inner layer portion 11 m is increased, theinternal stress produced by the difference in the coefficient of thermalcontraction between the dielectric layers and the conductive layers 13during the firing step is not significantly increased. Accordingly, byincreasing the width W₁ of the conductive layers 13 while maintainingthe size of the side gaps 12 c without increasing the number of layerswithin the inner layer portion 11 m, it is possible to significantlyreduce or prevent the occurrence of cracks caused by an internal stressproduced by the difference in the coefficient of thermal contractionbetween the dielectric layers 12 and the conductive layers 13 whilesecuring a sufficient electrostatic capacitance of the capacitor 10.

As described above, the total height of the height h₁ of the first outerlayer portion 12 b ₁ and height h₂ of the second outer layer portion 12b ₂ is smaller than the height T₁ of the inner layer portion 11 m. It isthus possible to secure the electrostatic capacitance per unit volume ofthe capacitor 10.

As described above, the second outer layer portion 12 b ₂ is greaterthan the first outer layer portion 12 b ₁. Thus, cracks produced in thedielectric layers 12 of the capacitor 10 caused by an external stressproduced when a substrate having the capacitor 10 mounted thereon isdeflected due to an external force may be prevented from reaching theconductive layers 13. More specifically, the difference between theheight h₂ of the second outer layer portion 12 b ₂ and the height h₁ ofthe first outer layer portion 12 b ₁ is equal to or greater than about10 μm. By forming the height h₂ of the second outer layer portion 12 b ₂to be about 90 μm or greater, it is possible to prevent theabove-described cracks from reaching the conductive layers 13.

However, if the height h₂ of the second outer layer portion 12 b ₂ isexcessively large, the internal stress produced by the difference in thecoefficient of thermal contraction between the dielectric layers 12 andthe conductive layers 13 during the firing step is increased, and theelectrostatic capacitance per unit volume of the capacitor 10 isdecreased. By setting the height h₂ of the second outer layer portion 12b ₂ to be equal to or smaller than about ¼ of the height T₁ of the innerlayer portion 11 m, it is possible to significantly reduce or prevent anincrease in the internal stress produced by the difference in thecoefficient of thermal contraction between the dielectric layers 12 andthe conductive layers 13 during the firing step and also tosignificantly reduce or prevent a decrease in the electrostaticcapacitance per unit volume of the capacitor 10.

As described above, the height T₀ of the body 11 is preferably greaterthan about ⅓ of the length L₀ of the body 11 in the length direction Land is also preferably smaller than about ½ of the length L₀ of the body11. With this configuration, while the height of the body 11 isdecreased, the possibility that the capacitor 10, which is thin, will bebroken due to the insufficient strength when an external force isapplied to the capacitor 10 can be reduced.

As described above, the height T₀ of the body 11 is preferably smallerthan the width W₁ of the inner layer portion 11 m. With thisconfiguration, the space factor of the conductive layers 13 within thebody 11 is increased, and accordingly, the Young's modulus is increased.It is thus possible to reduce the possibility that the capacitor 10,which is thin, will be broken due to the insufficient strength when anexternal force is applied to the capacitor 10.

As described above, the width W₀ of the body 11 is preferably greaterthan about 0.9 mm and the height T₀ of the body 11 is preferably smallerthan about 0.9 mm. With this configuration, the capacitor 10 can besuitably used in a thin electronic device.

As described above, the maximum width of the side gaps 12 c ispreferably greater than the height h₁ of the first outer layer portion12 b ₁. If the first outer layer portion 12 b ₁ is thin, it is possibleto reduce the internal stress which is produced in the firing step dueto the difference in the coefficient of thermal contraction between thedielectric layers and the conductive layers and which acts on theboundary between the inner layer portion 11 m and the first outer layerportion 12 b ₁. Thus, the occurrence of cracks (delamination) at theboundary between the inner layer portion 11 m and the first outer layerportion 12 b ₁ can be significantly reduced or prevented.

If the maximum width of the side gaps 12 c is increased, whenpressure-bonding a set of mother sheets, the pressure is more likely tobe applied to the plurality of dielectric layers 12 positioned in theside gaps 12 c, thus enhancing the adherence of the dielectric layers 12in the side gaps 12 c. As a result, it is possible to significantlyreduce or prevent the occurrence of cracks (delamination) in thedielectric layers 12 positioned in the side gaps 12 c.

As described above, the average width ((W₀−W₁)/2) of the side gaps 12 cis preferably greater than the height h₁ of the first outer layerportion 12 b ₁. The half of the total width of the two adjacent sidegaps 12 c of two adjacent bodies 11 divided from the mother bodycorresponds to the average width ((W₀−W₁)/2). Accordingly, if theaverage width ((W₀−W₁)/2) of the side gaps 12 c is set to be greaterthan the height h₁ of the first outer layer portion 12 b ₁, whenpressure-bonding a set of mother sheets, the pressure is more likely tobe applied to the plurality of dielectric layers 12 positioned in theside gaps 12 c, thus enhancing the adherence of the dielectric layers 12positioned in the side gaps 12 c. As a result, it is possible tosignificantly reduce or prevent the occurrence of cracks (delamination)in the dielectric layers 12 positioned in the side gaps 12 c. That is,even if there is a difference between the width of the side gap 12 cclose to the first side surface 115 and that close to the second sidesurface 116, the effect of significantly reducing or preventing theoccurrence of cracks (delamination) can be stably exhibited.

As described above, the maximum width or the average width ((W₀−W₁)/2)of the side gaps 12 c is more preferably greater than about 30 μm andsmaller than about 90 μm, for example. If the maximum width or theaverage width ((W₀−W₁)/2) of the side gaps 12 c is greater than about 30μm, the occurrence of cracks (delamination) at the boundary between theinner layer portion 11 m and the second outer layer portion 12 b ₂ isreliably significantly reduced or prevented. If the maximum width or theaverage width ((W₀−W₁)/2) of the side gaps 12 c is equal to or greaterthan about 90 μm, the electrostatic capacitance of the capacitor 10becomes too small. That is, by setting the maximum width or the averagewidth ((W₀−W₁)/2) of the side gaps 12 c to be smaller than about 90 μm,a sufficient electrostatic capacitance of the capacitor 10 is secured.

A capacitor mount body including the capacitor 10 of the first preferredembodiment mounted thereon will be described below with reference toFIG. 7.

FIG. 7 is a sectional view illustrating a capacitor mount body 10 x ofthe first preferred embodiment. The capacitor mount body 10 x includesthe capacitor 10 and a substrate 1, such as a circuit board, used tomount the capacitor 10 thereon. The capacitor 10 is mounted on thesubstrate 1 such that the second main surface 112 faces the substrate 1.

The configuration of the capacitor mount body 10 x will be discussedmore specifically. A pair of lands 20 is disposed on the surface of thesubstrate 1 such that the lands 20 are spaced apart from each other. Thetwo outer electrodes 14 of the capacitor 10 and the two lands 20 areelectrically connected to each other by solder 30, which is a bondingmedium. The bonding medium is not restricted to solder, and any bondingmaterial may be used as long as it is able to mechanically andelectrically connect the two outer electrodes 14 and the two lands 20.

A width W_(L) of the two lands 20 is smaller than the width W₀ of thebody 11. The width W_(L) of the two lands 20 is preferably smaller thanthe width W₁ of the inner layer portion 11 m. By setting the width W_(L)of the two lands 20 to be smaller than the width W₀ of the body 11, thetwo outer electrodes 14 are subjected to a compressive stress appliedfrom the solder 30 in the width direction W of the body 11. Thiscompressive stress further acts on the second outer layer portion 12 b₂. Accordingly, the internal stress acting on the boundary between theinner layer portion 11 m and the second outer layer portion 12 b ₂ isrelaxed, thus significantly reducing or preventing the occurrence ofcracks (delamination) at this boundary.

If the width W_(L) of the two lands 20 is smaller than the width W₁ ofthe inner layer portion 11 m, the compressive stress acting on thesecond outer layer portion 12 b ₂ is increased. Accordingly, theinternal stress acting on the boundary between the inner layer portion11 m and the second outer layer portion 12 b ₂ is further relaxed, thusfurther significantly reducing or preventing the occurrence of cracks(delamination) at this boundary.

A capacitor series including a plurality of capacitors of the firstpreferred embodiment will be described below with reference to FIGS. 8and 9.

FIG. 8 is a plan view of a capacitor series 10 s according to the firstpreferred embodiment. FIG. 9 is a sectional view taken along line IX-IXof FIG. 8.

As shown in FIGS. 8 and 9, the capacitor series 10 s includes aplurality of capacitors 10 and a package 4. The package 4 includes anelongated carrier tape 5 and a cover tape 6. The carrier tape 5 includesa plurality of cavities 5 h disposed apart from each other and storingthe plurality of capacitors 10 therein. The cover tape 6 is attached tothe carrier tape 5 so as to cover the plurality of cavities 5 h. Theplurality of capacitors 10 are stored in the respective cavities 5 hsuch that the second main surfaces 112 face bottom sides 5 b of therespective cavities 5 h.

The plurality of capacitors 10 included in the capacitor series 10 s areextracted from the package 4 one by one and are mounted on the substrate1. More specifically, in the state in which the cover tape 6 is removedfrom the carrier tape 5, by sucking and holding the capacitors 10 at theside of the first main surfaces 111, the capacitors 10 are removed fromthe carrier tape 5 one by one and are mounted on the substrate 1. As aresult, the capacitors 10 are mounted on the substrate 1 with the secondmain surfaces 112 facing the substrate 1.

That is, by using the capacitor series 10 s of the first preferredembodiment, it is possible to easily manufacture the capacitor mountbody 10 x of the first preferred embodiment.

A capacitor and a capacitor mount body according to a second preferredembodiment will be described below with reference to the drawings. Themajor difference between the capacitor and the capacitor mount body ofthe second preferred embodiment and those of the first preferredembodiment is the configuration of the second outer layer portion. Theconfigurations of the other elements of the second preferred embodimentwill not be explained.

Second Preferred Embodiment

FIG. 10 is an external perspective view of a capacitor 10 a according tothe second preferred embodiment of the present invention. FIGS. 11 and12 are sectional views taken along lines XI-XI and XII-XII,respectively, of FIG. 10. FIGS. 13 and 14 are sectional views takenalong lines XIII-XIII and XIV-XIV, respectively, of FIG. 11. In FIGS. 10through 14, the length direction of a body 11 is indicated by L, thewidth direction thereof is indicated by W, and the height directionthereof is indicated by T.

As shown in FIGS. 10 through 14, the capacitor 10 a includes the body 11and two outer electrodes 14. The body 11 includes a plurality ofdielectric layers 12 and a plurality of conductive layers 13 stacked oneach other, and includes first and second main surfaces 111 and 112opposing each other in the stacking direction. The two outer electrodes14 are disposed on some surfaces of the body 11 and are electricallyconnected to all the conductive layers 13.

The plurality of dielectric layers 12 include a plurality of firstdielectric layers 12 x and a second dielectric layer 12 y, which areformed from ceramic green sheets made of different compositions, whichwill be discussed later.

A first outer layer portion 12 b ₁ includes a first dielectric layer 12x positioned closest to the first main surface 111 among the pluralityof dielectric layers 12. A second outer layer portion 12 b ₂ includes anouter portion 12 b ₂₂ and an inner portion 12 b ₂₁. The outer portion 12b ₂₂ includes a second dielectric layer 12 y, which is the dielectriclayer positioned closest to the second main surface 112 among theplurality of dielectric layers 12. The inner portion 12 b ₂₁ includesthe first dielectric layer 12 x positioned adjacent to the surface ofthe outer portion 12 b ₂₂ closer to the first main surface 111. Theconfiguration of the first outer layer portion 12 b ₁ is not restrictedto that discussed above. The first outer layer portion 12 b ₁ mayinclude an outer portion including a second dielectric layer 12 ypositioned closest to the first main surface 111 and an inner portionincluding a first dielectric layer 12 x positioned adjacent to thesurface of the outer portion closer to the second main surface 112.

In the inner layer portion 11 m, some of the plurality of dielectriclayers 12 x and all the conductive layers 13 are alternately stacked oneach other. That is, the inner layer portion 11 m includes all theconductive layers 13. All the conductive layers 13 are preferablyrectangular or substantially rectangular, as viewed from above.

In the second preferred embodiment, all the conductive layers 13preferably are electrically connected to either one of the two outerelectrodes 14. Alternatively, at least some of the conductive layers 13may be electrically connected to one of the two outer electrodes 14.That is, among the plurality of conductive layers 13, there may be someconductive layers 13 that are not electrically connected to any of thetwo outer electrodes 14.

The two outer electrodes 14 are disposed at both ends of the body 11 inthe length direction L. More specifically, one of the two outerelectrodes 14 is disposed at one end of the body 11 close to the firstend surface 113 in the length direction L, while the other one of thetwo outer electrodes 14 is disposed at the other end of the body 11close to the second end surface 114 in the length direction L. In thesecond preferred embodiment, one of the two outer electrodes 14 extendsfrom the first end surface 113 continuously to the first and second mainsurfaces 111 and 112 and to the first and second side surfaces 115 and116. The other one of the two outer electrodes 14 extends from thesecond end surface 114 continuously to the first and second mainsurfaces 111 and 112 and to the first and second side surfaces 115 and116. However, the arrangement of the two outer electrodes 14 is notrestricted to that described above. The two outer electrodes 14 may bedisposed on some surfaces of the body 11 so that they can beelectrically connected to the plurality of conductive layers 13 and sothat the capacitor 10 a can be mounted.

One of the two outer electrodes 14 is connected to some of the pluralityof conductive layers 13 on the first end surface 113, while the otherone of the two outer electrodes 14 is connected to the remainingconductive layers 13 on the second end surface 114. The conductivelayers 13 connected to the first end surface 113 and the remainingconductive layers 13 connected to the second end surface 114 arealternately stacked on each other such that they face each other with afirst dielectric layer 12 x therebetween in the inner layer portion 11m.

As shown in FIG. 12, the height T₁ of the inner layer portion 11 m inthe stacking direction of the body 11 is smaller than the width W₁ ofthe inner layer portion 11 m where the plurality of conductive layers 13are positioned in the width direction W of the body 11 in which thefirst and second side surfaces 115 and 116 are connected to each otherwith the shortest distance.

The height h₂₂ of the outer portion 12 b ₂₂ is equal to or greater thanthe height h₂₁ of the inner portion 12 b ₂₁. The height h₂₂ of the outerportion 12 b ₂₂ is preferably about 30 μm or greater, for example, whichwill be discussed later. The height h₂₁ of the inner portion 12 b ₂₁ ispreferably about 20 μm or greater, for example, which will be discussedlater.

The second outer layer portion 12 b ₂ is thicker than the first outerlayer portion 12 b ₁. That is, the height h₂ of the second outer layerportion 12 b ₂ is greater than the height h₁ of the first outer layerportion 12 b ₁. The height h₂₁ of the inner portion 12 b ₂₁ may be equalto or smaller than the height h₁ of the first outer layer portion 12 b₁.

It is preferable that, in the width direction W of the body 11, themaximum width of side gaps 12 c, which is the distance between each ofthe first and second side surfaces 115 and 116 and the inner layerportion 11 m, be greater than the height h₁ of the first outer layerportion 12 b ₁. It is also preferable that the average width ((W₀−W₁)/2)of the side gaps 12 c be greater than the height h₁ of the first outerlayer portion 12 b ₁. It is more preferable that the maximum width orthe average width ((W₀−W₁)/2) of the side gaps 12 c be greater thanabout 30 μm and smaller than about 90 μm, for example. It is alsopreferable that the maximum width of the side gaps 12 c be greater thanthe height h₂₁ of the inner portion 12 b ₂₁.

The configuration of each of the elements defining the capacitor 10 awill be described in detail. The dielectric layers 12 each contain aperovskite compound expressed by ABO₃ (“A” contains Ba, and “B” containsTi, and O is oxygen) as a principal component. That is, the plurality offirst dielectric layers 12 x and the second dielectric layer 12 y eachcontain barium titanate (BaTiO₃) as a principal component.

The plurality of dielectric layers 12 each contain Si as a secondarycomponent. Si is contained in the dielectric layers 12 by adding a Sicompound, such as glass or SiO₂, as a secondary component to aperovskite compound expressed by ABO₃ as a principal component. Anothercompound, such as a Mn compound, an Mg compound, a Co compound, a Nicompound, or a rare earth compound, may be added to a perovskitecompound expressed by ABO₃.

The composition ratio of Si to Ti of the second dielectric layer 12 ydefining the outer portion 12 b ₂₂ is higher than that of the firstdielectric layers 12 x included in the inner layer portion 11 m, thefirst dielectric layer 12 x defining the first outer layer portion 12 b₁, and the first dielectric layer 12 x defining the inner portion 12 b₂₁. The composition ratio of Si and other components to Ti may berepresented by a molar ratio. In the following description, thecomposition ratio will be referred to as the “molar ratio”. The molarratio of Si to Ti of each of the dielectric layers 12 may be measured byusing a wavelength-dispersive X-ray spectrometer (WDX).

The molar ratio of Si to Ti of the second dielectric layer 12 y definingthe outer portion 12 b ₂₂ is preferably about 1.3 to 3.0 mol percent(%), for example. If the molar ratio of Si to Ti of the seconddielectric layer 12 y forming the outer portion 12 b ₂₂ is lower thanabout 1.3 mol % or higher than about 3.0 mol %, the reliability of theouter portion 12 b ₂₂ may be impaired.

The molar ratio of Si to Ti of the second dielectric layer 12 y definingthe outer portion 12 b ₂₂ is preferably higher than that of the firstdielectric layer 12 x forming the inner portion 12 b ₂₁ by about 0.4 mol% or higher, and more preferably, by about 0.8 mol % or higher, forexample.

The outer portion 12 b ₂₂ includes a boundary region 12 z adjacent tothe inner portion 12 b ₂₁ which has a higher content of Si than acentral region 12 m of the outer portion 12 b ₂₂. A surface layersection 12 s of the outer portion 12 b ₂₂ close to the second mainsurface 112 also has a higher content of Si than the central region 12 mof the outer portion 12 b ₂₂. The boundary region 12 z and the surfacelayer section 12 s of the outer portion 12 b ₂₂ having a high contentratio of Si may be identified by element mapping created by using afield emission wavelength-dispersive X-ray spectrometer (FE-WDX).

A manufacturing method for the capacitor 10 a according to the secondpreferred embodiment of the present invention will be described belowwith reference to FIGS. 15 through 18.

FIG. 15 is a flowchart illustrating a non-limiting example of amanufacturing method according to the second preferred embodiment. Inthis manufacturing method, a plurality of capacitors 10 a aremass-produced at one time together in the following manner. Elementswhich will form a plurality of capacitors 10 a are processed togetheruntil a halfway point through a manufacturing process so as to fabricatea mother body. Then, the mother body is divided into individual flexiblebodies. The individual flexible bodies are then processed, thusmanufacturing a plurality of capacitors 10 a.

The manufacturing method will be discussed below more specifically withreference to FIG. 15. In step S11, a first ceramic slurry is preparedfirst. More specifically, a ceramic powder, a binder, and a solvent aremixed at a predetermined mixing ratio so as to form the first ceramicslurry.

Then, in step S12, first ceramic green sheets are formed. Morespecifically, the first ceramic slurry is formed into a sheet shape on acarrier film by using a die coater, a gravure coater, or a micro gravurecoater, thus forming the first ceramic green sheets.

Then, in step S13, mother sheets are formed. More specifically, aconductive paste is printed on each first ceramic green sheet by usingscreen printing or gravure printing such that a predetermined conductivepattern is formed on the first ceramic green sheet. As a result, amother sheet, which is a first ceramic green sheet having apredetermined conductive pattern thereon, is formed.

Mother sheets formed in step S13 will be discussed below in detail. FIG.16 is an exploded perspective view illustrating the multilayer structureof a set of unit sheets, which will define a partial body 11 p of thecapacitor 10 a of the second preferred embodiment without the outerportion 12 b ₂₂.

As shown in FIG. 16, the partial body 11 p includes a set of a pluralityof unit sheets 120 a, 130 a, and 130 b which are configured differently.More specifically, the plurality of unit sheets 120 a, 130 a, and 130 bare stacked on each other in a predetermined order and are thenpressure-bonded and fired so as to fabricate the partial body 11 p.

Each unit sheet 120 a is constituted only by a ceramic base member 12 xron which no conductive pattern is formed. The unit sheet 120 a defines afirst dielectric layer 12 x of the first outer layer portion 12 b ₁ orthe inner portion 12 b ₂₁ after the firing step is performed.

The unit sheets 130 a and 130 b are each constituted by a ceramic basemember 12 xr on which a conductive pattern 13 r having a predeterminedshape is provided. The conductive patterns 13 r of the unit sheets 130 aand 130 b define the conductive layers 13 within the inner layer portion11 m after the firing step is performed. The ceramic base members 12 xrof the unit sheets 130 a and 130 b define the first dielectric layers 12x within the inner layer portion 11 m after the firing step isperformed.

The layout of the mother sheet is as follows. By using each of the unitsheets 130 a and 130 b shown in FIG. 16 as a unit, a plurality of unitsheets having the same configuration as that of the unit sheet 130 a or130 b are two-dimensionally arranged in a matrix.

Since the unit sheets 130 a and 130 b have the same configuration, unitsheets having the same conductive pattern may be used as a mother sheet.In a step of stacking a set of mother sheets, which will be discussedlater, mother sheets having the same conductive pattern are displacedfrom each other by half pitch, thus obtaining the multilayer structureof the unit sheets 130 a and 130 b shown in FIG. 16.

As mother sheets, not only mother sheets having the conductive pattern13 r, but also first ceramic green sheets which are formed without beingsubjected to step S13 are also prepared.

Then, referring back to FIG. 15, in step S14, the mother sheets arestacked. More specifically, by stacking the plurality of mother sheetsaccording to a predetermined rule, the above-described units arepositioned within a set of the stacked mother sheets so that themultilayer structure shown in FIG. 16 can be obtained.

Then, in step S15, the set of stacked mother sheets is pressure-bonded.FIG. 17 is a sectional view illustrating a state in which the set ofmother sheets are being pressure-bonded. In FIG. 17, the set of mothersheets corresponding to only one partial body 11 p is shown. In thesecond preferred embodiment, as shown in FIG. 17, a plurality of mothersheets defining the first outer layer portion 12 b ₁, a plurality ofmother sheets defining the inner layer portion 11 m, and a plurality ofmother sheets defining the inner portion 12 b ₂₁ are stacked on eachother in this order so as to form the set of mother sheets.

A flat die 91 is pressed against the mother sheets defining the innerportion 12 b ₂₁ along the stacking direction, as indicated by an arrow92 in FIG. 17, thus pressure-bonding the set of mother sheets placed ona base 90.

In step S21, second ceramic slurry is prepared. More specifically, aceramic powder, a binder, and a solvent are mixed at a predeterminedmixing ratio so as to form the second ceramic slurry. The amount of Sicontained in the second ceramic slurry is greater than that in the firstceramic slurry.

Then, in step S22, second ceramic green sheets are formed. Morespecifically, the second ceramic slurry is formed into a sheet shape ona carrier film by using a die coater, a gravure coater, or a microgravure coater, thus forming a plurality of second ceramic green sheets.

Then, in step S23, the plurality of second ceramic green sheets arestacked on the set of mother sheets pressure-bonded in step S15. Morespecifically, the plurality of second ceramic green sheets uniquely madeof a ceramic base member 12 yr defining the second dielectric layer 12 yof the outer portion 12 b ₂₂ are stacked on the mother sheets formingthe inner portion 12 b ₂₁. Instead of stacking the plurality of secondceramic green sheets uniquely made of a ceramic base member 12 yr, apaste containing the second ceramic slurry may be applied onto themother sheets defining the inner portion 12 b ₂₁.

Then, in step S24, the set of mother sheets pressure-bonded in step S15and the plurality of second ceramic green sheets are beingpressure-bonded. FIG. 18 is a sectional view illustrating a state inwhich the set of mother sheets and the plurality of second ceramic greensheets are being pressure-bonded. In FIG. 18, the set of mother sheetsand the plurality of second ceramic green sheets corresponding to onlyone flexible body 11 q are shown. In FIG. 18, a flat die 91 is pressedagainst the mother sheets defining the outer portion 12 b ₂₂ along thestacking direction of the set of mother sheets, as indicated by an arrow92, thus pressure-bonding the set of mother sheets and the plurality ofsecond ceramic green sheets. As a result, a mother body is fabricated.

Then, in step S25, the mother body is divided. More specifically, themother body is press-cut or cut with a dicing machine in a matrix intothe flexible bodies 11 q.

Then, in step S26, the flexible bodies 11 q are fired. Morespecifically, the flexible bodies 11 q are heated to a predeterminedtemperature so as to fire the ceramic dielectric material and theconductive material. The firing temperature is set suitably inaccordance with the type of ceramic dielectric material and the type ofconductive material, and may be set within a range of about 900° C. toabout 1300° C., for example.

Then, in step S27, the flexible bodies 11 q are barrel-polished. Morespecifically, the flexible bodies 11 q subjected to firing are sealedwithin a small box called a barrel, together with media balls having ahigher hardness than the ceramic material. Then, by rotating the barrel,the flexible bodies 11 q are polished. By performing thisbarrel-polishing, the outer surfaces (in particular, corners and ridges)of the flexible bodies 11 q are curved and rounded. As a result, thebody 11 is formed.

Then, in step S28, outer electrodes are formed. More specifically, aconductive paste is applied to an end portion including the first endsurface 113 and an end portion including the second end surface 114 ofthe body 11 so as to form a metal film, and then, the metal film isfired. Then, the metal film is sequentially Ni-plated and Sn-plated. Asa result, the two outer electrodes 14 are formed on the outer surfacesof the body 11.

Through the above-described series of steps, the capacitor 10 aconfigured as shown in FIGS. 10 through 14 is manufactured.

In the capacitor 10 a of the second preferred embodiment, the molarratio of Si to Ti of the second dielectric layer 12 y defining the outerportion 12 b ₂₂ is higher than that of the first dielectric layers 12 xincluded in the inner layer portion 11 m and the first dielectric layer12 x defining the inner portion 12 b ₂₁. That is, the outer portion 12 b₂₂ has a higher content of Si than the inner portion 12 b ₂₁. In afiring step, the coefficient of thermal contraction of a dielectriclayer having a higher content of Si is higher. Accordingly, in thefiring step, the coefficient of thermal contraction of the outer portion12 b ₂₂ is higher than that of the inner portion 12 b ₂₁. Thus, thecoefficient of thermal contraction of the outer portion 12 b ₂₂ iscloser to that of the conductive layers 13 of the inner layer portion 11m.

In the capacitor 10 a, it is possible to reduce an internal stress whichis produced in the firing step due to the difference in the coefficientof thermal contraction between the dielectric layers and the conductivelayers and which acts on the boundary between the inner layer portion 11m and the second outer layer portion 12 b ₂. Thus, the occurrence ofcracks (delamination) at the boundary between the inner layer portion 11m and the second outer layer portion 12 b ₂ is significantly reduced orprevented.

The molar ratio of Si to Ti of the second dielectric layer 12 y definingthe outer portion 12 b ₂₂ preferably is higher than that of the firstdielectric layer 12 x defining the inner portion 12 b ₂₁ by about 0.4mol % or higher, for example. With this configuration, the occurrence ofcracks (delamination) at the boundary between the inner layer portion 11m and the second outer layer portion 12 b ₂ is effectively significantlyreduced or prevented. The molar ratio of Si to Ti of the outer portion12 b ₂₂ is preferably higher than that of the inner portion 12 b ₂₁ byabout 0.8 mol % or higher, for example. With this configuration, theoccurrence of cracks at the boundary between the inner layer portion 11m and the second outer layer portion 12 b ₂ can be significantly reducedor prevented even more effectively.

As described above, the height of the outer portion 12 b ₂₂ is equal toor greater than that of the inner portion 12 b ₂₁. With thisconfiguration, the stress relaxing effect exhibited by the thermalcontraction of the outer portion 12 b ₂₂ is more likely to be producedat the boundary between the inner layer portion 11 m and the secondouter layer portion 12 b ₂.

The height h₂₂ of the outer portion 12 b ₂₂ preferably is about 30 μm orgreater, for example. With this configuration, it is possible to securea sufficient contraction force which acts on the inner portion 12 b ₂₁by the thermal contraction of the outer portion 12 b ₂₂.

The height h₂₁ of the inner portion 12 b ₂₁ preferably is about 20 μm orgreater, for example. With this configuration, the diffusion of Sicontained in the outer portion 12 b ₂₂ into the inner layer portion 11 mis significantly reduced or prevented. If the content ratio of Si in theinner layer portion 11 m becomes too high, the grain growth of ceramicparticles in the first dielectric layers 12 x included in the innerlayer portion 11 m accelerates excessively in the firing step, thusreducing the withstand voltage characteristics of the first dielectriclayers 12 x. As a result, the inner layer portion 11 m is more likely tobe short-circuited. However, by setting the height h₂₁ of the innerportion 12 b ₂₁ to be about 20 μm or greater, for example, the withstandvoltage characteristics of the first dielectric layers 12 x included inthe inner layer portion 11 m are maintained, and thus, the occurrence ofshort-circuiting of the inner layer portion 11 m is significantlyreduced or prevented.

As described above, the height h₂₁ of the inner portion 12 b ₂₁ may beequal to or smaller than the height h₁ of the first outer layer portion12 b ₁. Even if the inner portion 12 b ₂₁ is thin, the presence of theouter portion 12 b ₂₂ makes it possible to significantly reduce orprevent the occurrence of short-circuiting in the inner layer portion 11m caused by the entry of moisture into the inner layer portion 11 m viathe inner portion 12 b ₂₁.

As described above, the maximum width of the side gaps 12 c ispreferably greater than the height h₁ of the first outer layer portion12 b ₁. If the first outer layer portion 12 b ₁ is thin, it is possibleto reduce an internal stress which is produced during the firing stepdue to the difference in the coefficient of thermal contraction betweenthe dielectric layers and the conductive layers and which acts on theboundary between the inner layer portion 11 m and the first outer layerportion 12 b ₁. Thus, the occurrence of cracks (delamination) at theboundary between the inner layer portion 11 m and the first outer layerportion 12 b ₁ is significantly reduced or prevented.

If the maximum width of the side gaps 12 c is set to be large, whenpressure-bonding a set of mother sheets, the pressure is more likely tobe applied to the plurality of first dielectric layers 12 x positionedin the side gaps 12 c, thus enhancing the adherence of the firstdielectric layers 12 x in the side gaps 12 c. As a result, it ispossible to significantly reduce or prevent the occurrence of cracks(delamination) in the first dielectric layers 12 x positioned in theside gaps 12 c.

As described above, the average width ((W₀−W₁)/2) of the side gaps 12 cis preferably greater than the height h₁ of the first outer layerportion 12 b ₁. The half of the total width of the two adjacent sidegaps 12 c of two adjacent bodies 11 divided from the mother bodycorresponds to the average width ((W₀−W₁)/2). Accordingly, if theaverage width ((W₀−W₁)/2) of the side gaps 12 c is set to be greaterthan the height h₁ of the first outer layer portion 12 b ₁, whenpressure-bonding a set of mother sheets, the pressure is more likely tobe applied to the plurality of first dielectric layers 12 x positionedin the side gaps 12 c, thus enhancing the adherence of the firstdielectric layers 12 x positioned in the side gaps 12 c. As a result, itis possible to significantly reduce or prevent the occurrence of cracks(delamination) in the first dielectric layers 12 x positioned in theside gaps 12 c. That is, even if there is a difference between the widthof the side gap 12 c close to the first side surface 115 and that closeto the second side surface 116, both of the effect of significantlyreducing or preventing the occurrence of cracks (delamination) and theeffect of significantly reducing or preventing the occurrence ofshort-circuiting in the inner layer portion 11 m are reliably achieved.

As described above, the maximum width of the side gaps 12 c ispreferably greater than the height h₂₁ of the inner portion 12 b ₂₁. Ifthe inner portion 12 b ₂₁ is thin, a contraction force exhibited by thethermal contraction of the outer portion 12 b ₂₂ is likely to act on theinner portion 12 b ₂₁. It is thus possible to effectively reduce aninternal stress which is produced during the firing step due to thedifference in the coefficient of thermal contraction between thedielectric layers and the conductive layers and which acts on theboundary between the inner layer portion 11 m and the inner portion 12 b₂₁. As a result, the occurrence of cracks (delamination) at the boundarybetween the inner layer portion 11 m and the second outer layer portion12 b ₂ is significantly reduced or prevented.

As described above, the maximum width or the average width ((W₀−W₁)/2)of the side gaps 12 c is more preferably greater than about 30 μm andsmaller than about 90 μm, for example. If the maximum width or theaverage width ((W₀−W₁)/2) of the side gaps 12 c is greater than about 30μm, for example, the occurrence of cracks (delamination) at the boundarybetween the inner layer portion 11 m and the inner portion 12 b ₂₁ isreliably significantly reduced or prevented. If the maximum width or theaverage width ((W₀−W₁)/2) of the side gaps 12 c is equal to or greaterthan about 90 μm, the electrostatic capacitance of the capacitor 10becomes too small. That is, by setting the maximum width or the averagewidth ((W₀−W₁)/2) of the side gaps 12 c to be smaller than about 90 μm,for example, a sufficient electrostatic capacitance of the capacitor 10a is secured.

As described above, since each of the plurality of first dielectriclayers 12 x and the second dielectric layer 12 y contains bariumtitanate as a principal component, chemical bonding at the interfacebetween the inner portion 12 b ₂₁ and the outer portion 12 b ₂₂ isstrengthened, thus enhancing the adherence therebetween. As a result, itis possible to significantly reduce or prevent the occurrence of cracks(delamination) at the boundary region in the outer portion 12 b ₂₂.

As described above, the boundary region 12 z in the outer portion 12 b₂₂ has a higher content of Si than the central region 12 m of the outerportion 12 b ₂₂ since Si is concentrated in this boundary region 12 zafter moving from the outer portion 12 b ₂₂ or the inner portion 12 b₂₁. The surface layer section 12 s of the outer portion 12 b ₂₂ close tothe second main surface 112 also has a higher content of Si than thecentral region 12 m of the outer portion 12 b ₂₂.

A description will be given below of how to set the content ratio of Siof the boundary region 12 z in the outer portion 12 b ₂₂ and the surfacelayer section 12 s of the outer portion 12 b ₂₂ to be higher than thatof the central region 12 m of the outer portion 12 b ₂₂. The firing stepfor the capacitor 10 a is performed at a temperature and in a gaseousatmosphere in which Si segregates from grain boundaries of ceramicparticles. Then, in the outer portion 12 b ₂₂ containing a greateramount of Si, the grain growth of ceramic particles is encouraged, andSi segregates from the grain boundaries of coarsened ceramic particles.Segregated Si moves along the grain boundaries of the ceramic particlesand concentrates toward the boundary region 12 z in the outer portion 12b ₂₂ and the surface layer section 12 s of the outer portion 12 b ₂₂. Asa result, the content ratio of Si of the boundary region 12 z and thatof the surface layer section 12 s of the outer portion 12 b ₂₂ becomehigher than that of the central region 12 m of the outer portion 12 b₂₂.

The content ratio of Si of the boundary region 12 z in the outer portion12 b ₂₂ is higher than that of the central region 12 m of the outerportion 12 b ₂₂, thus improving the adhesion force between the outerportion 12 b ₂₂ and the inner portion 12 b ₂₁. The reason for this maybe as follows. Si which has moved along the grain boundaries of theceramic particles as described above fills many small gaps at theinterface between the outer portion 12 b ₂₂ and the inner portion 12 b₂₁ so as to bond them each other. Accordingly, by separately forming theouter portion 12 b ₂₂ and the inner portion 12 b ₂₁, small gaps arecreated at the interface between the outer portion 12 b ₂₂ and the innerportion 12 b ₂₁. This encourages the concentration of segregated Si inthe boundary region 12 z, thus improving the adhesion force between theouter portion 12 b ₂₂ and the inner portion 12 b ₂₁.

The content ratio of Si of the surface layer section 12 s of the outerportion 12 b ₂₂ close to the second main surface 112 is higher than thatof the central region 12 m of the outer portion 12 b ₂₂, thussignificantly reducing or preventing a decrease in the mechanicalstrength of the body 11 when forming the outer electrodes 14. The reasonfor this is as follows. In the formation of the outer electrodes 14, ifglass components contained in the outer electrodes 14 react with theceramic dielectric material of the body 11, the mechanical strength ofthe body 11 is decreased. In this case, if an external force is appliedto the capacitor 10 a while the capacitor 10 a is being mounted or afterit has been mounted, cracks are likely to occur in the body 11 startingfrom the end of the contact area with the outer electrode 14 close tothe center of the body 11. However, if the content ratio of Si of theouter portion 12 b ₂₂ is high, the reaction of glass componentscontained in the outer electrodes 14 with the ceramic dielectricmaterial of the body 11 can be significantly reduced or prevented. As aresult, it is possible to significantly reduce or prevent a decrease inthe mechanical strength of the body 11 when forming the outer electrodes14.

In each of the plurality of dielectric layers 12, if a rare earthcompound is contained in a perovskite compound expressed by ABO₃, whichis a principal component, the molar ratio of a rare earth element to Tiof the first dielectric layers 12 x included in the inner layer portion11 m and the first dielectric layer 12 x defining the inner portion 12 b₂₁ is preferably higher than that of the second dielectric layer 12 yforming the outer portion 12 b ₂₂. That is, the inner layer portion 11 mand the inner portion 12 b ₂₁ preferably contain a greater amount ofrare earth element than the outer portion 12 b ₂₂.

As a rare earth element, Dy, Gd, Y, or La may be added for improving thefunctions of the capacitor 10 a. More specifically, by adding a rareearth element, it is possible to stabilize the capacitance temperaturecharacteristics and to prolong the life of the capacitor 10 a bymaintaining the insulation resistance (IR) value even under ahigh-temperature load.

A rare earth element is likely to concentrate in a grain boundary ofceramic particles or a segregation layer and also to elute towater-soluble flux. Accordingly, ceramic components containing a rareearth element may elute to an organic acid, such as adipic acid,contained in water-soluble flux used for soldering when mounting thecapacitor 10 a. In this case, cracks may occur in the outer layerportion 12 b ₂ of the body 11 which is embrittled as a result of theeluting of ceramic components.

Accordingly, the molar ratio of a rare earth element to Ti of the firstdielectric layers 12 x included in the inner layer portion 11 m and thefirst dielectric layer 12 x forming the inner portion 12 b ₂₁ ispreferably about 0.3 mol % or higher, and the molar ratio of a rareearth element to Ti of the second dielectric layer 12 y forming theouter portion 12 b ₂₂ is preferably lower than about 0.3 mol %, forexample.

By setting the molar ratio of a rare earth element to Ti of the firstdielectric layers 12 x included in the inner layer portion 11 m to beabout 0.3 mol % or higher, for example, it is possible to stabilize thecapacitance temperature characteristics and to prolong the life of thecapacitor 10 a by maintaining the insulation resistance (IR) value evenunder a high-temperature load.

By setting the molar ratio of a rare earth element to Ti of the seconddielectric layer 12 y defining the outer portion 12 b ₂₂ to be lowerthan about 0.3 mol %, for example, it is possible to significantlyreduce or prevent the occurrence of cracks in the outer portion 12 b ₂₂caused by the embrittlement of the outer portion 12 b ₂₂ as a result ofthe eluting of ceramic components from the outer portion 12 b ₂₂. Thesefeatures and advantages have been validated, as a result of conductingexperiments by changing the content of Dy used as a rare earth element.Advantages obtained by the use of Gd, Y, or La instead of Dy have alsobeen validated.

In each of the plurality of dielectric layers 12, if a Mn compound iscontained in a perovskite compound expressed by ABO₃, which is aprincipal component, the molar ratio of a Mn compound to Ti of the firstdielectric layers 12 x included in the inner layer portion 11 m, thefirst dielectric layer 12 x forming the first outer layer portion 12 b₁, and the first dielectric layer 12 x defining the inner portion 12 b₂₁ is preferably higher than that of the second dielectric layer 12 ydefining the outer portion 12 b ₂₂. That is, the inner layer portion 11m and the inner portion 12 b ₂₁ preferably contain a greater amount ofMn than the outer portion 12 b ₂₂.

The color of a dielectric layer containing a smaller amount of Mn isbrighter than that containing a greater amount of Mn. Accordingly, thecolor of the outer portion 12 b ₂₂ is brighter than that of the innerlayer portion 11 m, the first outer layer portion 12 b ₁, and the innerportion 12 b ₂₁, which contain a greater amount of Mn. It is thus easyto visually distinguish the first and second main surfaces 111 and 112of the capacitor 10 a from each other.

When observing the capacitor 10 a with an imaging camera, theorientations of the first and second main surfaces 111 and 112 of thecapacitor 10 a can be identified. Thus, when mounting the capacitor 10a, the orientation of the capacitor 10 a can be automatically set sothat the second main surface 112 will be a mounting surface.

For example, the molar ratio of Mn to Ti of the first dielectric layers12 x included in the inner layer portion 11 m, the first dielectriclayer 12 x defining the first outer layer portion 12 b ₁, and the firstdielectric layer 12 x defining the inner portion 12 b ₂₁ is preferablyabout 0.08 mol % or higher, and the molar ratio of Mn to Ti of thesecond dielectric layer 12 y defining the outer portion 12 b ₂₂ ispreferably lower than about 0.08 mol %, for example. These features andadvantages have been validated as a result of conducting experiments bychanging the content of Mn.

A capacitor mount body having the capacitor 10 a of the second preferredembodiment mounted thereon will be described below with reference toFIG. 19.

FIG. 19 is a sectional view illustrating a capacitor mount body 10 ax ofthe second preferred embodiment. The capacitor mount body 10 ax includesthe capacitor 10 a and a substrate 1, such as a circuit board, used tomount the capacitor 10 a thereon. The capacitor 10 a is mounted on thesubstrate 1 such that the second main surface 112 faces the substrate 1.

The configuration of the capacitor mount body 10 ax will be discussedmore specifically. A pair of lands 20 is disposed on the surface of thesubstrate 1 such that the lands 20 are spaced apart from each other. Thetwo outer electrodes of the capacitor 10 a and the two lands 20 areelectrically connected to each other by solder 30, which is a bondingmedium. The bonding medium is not restricted to solder, and any bondingmaterial may be used as long as it is able to mechanically andelectrically connect the two outer electrodes 14 and the two lands 20.

The width W_(L) of the two lands 20 is smaller than the width W₀ of thebody 11. The width W_(L) of the two lands 20 is preferably smaller thanthe width W₁ of the inner layer portion 11 m. By setting the width W_(L)of the two lands 20 to be smaller than the width W₀ of the body 11, thetwo outer electrodes 14 are subjected to a compressive stress appliedfrom the solder 30 in the width direction W of the body 11. Thiscompressive stress further acts on the inner portion 12 b ₂₁ via theouter portion 12 b ₂₂. Accordingly, the internal stress acting on theboundary between the inner layer portion 11 m and the second outer layerportion 12 b ₂ is relaxed, thus significantly reducing or preventing theoccurrence of cracks (delamination) at this boundary.

If the width W_(L) of the two lands 20 is smaller than the width W₁ ofthe inner layer portion 11 m, the compressive stress acting on the innerportion 12 b ₂₁ via the outer portion 12 b ₂₂ is increased. Accordingly,the internal stress acting on the boundary between the inner layerportion 11 m and the second outer layer portion 12 b ₂ is furtherrelaxed, thus further significantly reducing or preventing theoccurrence of cracks (delamination) at this boundary.

A capacitor according to a third preferred embodiment of the presentinvention will be described below. The capacitor of the third preferredembodiment is different from that of the second preferred embodimentonly in the configuration of the boundary region in the outer portion.Thus, the configurations of the other elements will not be explained.

Third Preferred Embodiment

The configuration of the boundary region of the outer portion 12 b ₂₂with the inner portion 12 b ₂₁ of the body 11 of the capacitor ispreferably implemented by a pressure-bonding method for a set of mothersheets. Accordingly, the pressure-bonding method for a set of mothersheets in the third preferred embodiment will first be described below.

FIG. 20 is a sectional view illustrating a state in which a set ofmother sheets defining the capacitor in the third preferred embodimentare being pressure-bonded. The set of mother sheets shown in FIG. 20 isthat as viewed from the same cross section as that shown in FIG. 17. InFIG. 20, the set of mother sheets corresponding to only two partialbodies 11 p is shown.

As shown in FIG. 20, in the third preferred embodiment, a plurality ofmother sheets defining the first outer layer portion 12 b ₁, a pluralityof mother sheets defining the inner layer portion 11 m, and a pluralityof mother sheets defining the inner portion 12 b ₂₁ are stacked on eachother in this order so as to form a set of mother sheets.

A flat die 91 and a rubber 93 attached to the bottom surface of the flatdie 91 are pressed against the mother sheets defining the inner portion12 b ₂₁ along the stacking direction, as indicated by an arrow 92 inFIG. 20, thus pressure-bonding the set of mother sheets placed on a base90.

In the set of mother sheets, the stacking density of the mother sheetsdefining the inner layer portion 11 m is higher than that of the mothersheets forming the side gaps 12 c. Accordingly, as indicated by thedotted lines 93 s in FIG. 20, the rubber 93 pressed against the set ofmother sheets is deformed and projected downward from positionscorresponding to the inner layer portion 11 m toward positionscorresponding to the side gaps 12 c. This causes the mother sheets atthe positions corresponding to the side gaps 12 c to be pressure-bondedto each other and to adhere to each other.

FIG. 21 is a sectional view illustrating a state in which the set ofpressure-bonded mother sheets and a plurality of second ceramic greensheets are being pressure-bonded. In FIG. 21, the set of mother sheetscorresponding to only two partial bodies 11 q is shown. The flat die 91is pressed against the mother sheets forming the outer portion 12 b ₂₂along the stacking direction, as indicated by the arrow 92, thuspressure-bonding the set of mother sheets and the plurality of secondceramic green sheets. As a result, a mother body is fabricated.

FIG. 22 is a sectional view illustrating a state in which the motherbody is divided. In FIG. 22, the mother body corresponding to only twopartial bodies 11 q is shown. As shown in FIG. 22, the second ceramicgreen sheets are deformed from positions corresponding to the innerlayer portion 11 m toward positions corresponding to the side gaps 12 cin accordance with the configuration of the top surface of the set ofpressure-bonded mother sheets, and are projected downward at thepositions corresponding to the side gaps 12 c toward the center of theflexible body 11 p in the stacking direction.

Accordingly, the boundary region 12 z at the side gaps 12 c includesbent portions 12 zw which incline toward the center of the flexible body11 q in the stacking direction.

By dividing the mother body on a cut line CL, a plurality of flexiblebodies 11 q are obtained. The subsequent steps are similar to those ofthe manufacturing method for the capacitor 10 a discussed in the secondpreferred embodiment.

In the capacitor of the third preferred embodiment, the adherencebetween the first dielectric layers 12 x positioned in the side gaps 12c is enhanced. As a result, it is possible to significantly reduce orprevent the occurrence of cracks (delamination) in the first dielectriclayers 12 x positioned in the side gaps 12 c.

Since the boundary region 12 z positioned in the side gaps 12 c includesbent portions 12 zw, the outer portion 12 b ₂₂ clamps the inner portion12 b ₂₁ therebetween via a pair of bent portions 12 zw. Accordingly, acontraction force exhibited by the thermal contraction of the outerportion 12 b ₂₂ is effectively applied to the inner portion 12 b ₂₁. Itis thus possible to effectively reduce an internal stress which isproduced during the firing step due to the difference in the coefficientof thermal contraction between the dielectric layers and the conductivelayers and which acts on the boundary between the inner layer portion 11m and the second outer layer portion 12 b ₂. As a result, the occurrenceof cracks (delamination) at the boundary between the inner layer portion11 m and the second outer layer portion 12 b ₂ is significantly reducedor prevented.

A description will be given below of an experiment for examining how theheight and the width of the body of a capacitor and the height and thewidth of an inner layer portion influence the occurrence of cracksduring a firing step for the capacitor.

Experiment

In this experiment, a total of four types of capacitors according tocomparative examples 1 through 3 and example 1 were fabricated.Conditions (design values) applied to all the four types of capacitorswill be discussed first.

For distinguishing the main surfaces and side surfaces of the body ofeach capacitor from each other from the outer configuration of the body,the height and the width of the body were set to be different by about20% or higher. The length of the body was about 1.65 mm and the lengthof the opposing conductive layers (the length of the inner layerportion) was about 1.47 mm.

The conditions set for the four types of capacitors according tocomparative examples 1 through 3 and example 1 are indicated in theTable below.

For the evaluation concerning the occurrence of cracks during the firingof the capacitors, ten samples of each of the four types of capacitorswere prepared. If the occurrence of cracks was observed in even one ofthe ten samples of each type of capacitor, the evaluation concerning theoccurrence of cracks in this type of capacitor was determined to be“BAD”, and if the occurrence of cracks was observed in none of the tensamples, the evaluation concerning the occurrence of cracks in this typeof capacitor was determined to be “GOOD”. The occurrence of cracks waschecked by exposing a WT cross section passing through the center of thebody of a capacitor by polishing the body and by observing the exposedWT cross section with an optical microscope.

TABLE Comparative Comparative Comparative Example 1 example 1 example 2example 3 Width of body 0.91 0.91 0.95 0.95 (μm) Height of body 0.710.71 1.1 1.1 (μm) Width of inner 0.81 0.57 0.85 0.85 layer portion (μm)Height of inner 0.58 0.58 0.84 0.97 layer portion (μm) Height of first40 40 40 40 outer layer portion (μm) Height of second 90 90 220 90 outerlayer portion (μm) Side gap (μm) 50 170 50 50 Number of layers 250 250360 415 stacked in inner layer portion Occurrence of GOOD GOOD BAD BADcracks

The Table above indicates the evaluation results of this experiment. Asindicated by the Table above, in the capacitors of example 1 andcomparative example 1 in which the height of the body was smaller thanthe width thereof, the occurrence of cracks during the firing of thecapacitors was significantly reduced or prevented. However, in thecapacitor of comparative example 1, since the height of the inner layerportion is greater than the width thereof, the electrostatic capacitancewas lower than that of example 1. Accordingly, only in the capacitor ofexample 1, the occurrence of cracks caused by an internal stressproduced by the difference in the coefficient of thermal contractionbetween dielectric layers and conductive layers was significantlyreduced or prevented while securing a sufficient electrostaticcapacitance.

Particularly, a preferred embodiment of the present invention iseffectively applicable to small capacitors in which the height of thesecond outer layer portion 12 b ₂ is about 50 μm or greater, theelectrostatic capacitance is about 10 μF or higher, the length of thebody 11 is about 2.0 mm or smaller, and the number of conductive layers13 to be stacked is about 250 or greater, for example.

Measurement methods for the thickness of a dielectric layer and that ofa conductive layer of a capacitor will be discussed below. FIG. 23illustrates an example of an enlarged image of a cross section of acapacitor observed with a scanning electron microscope (SEM). In FIG.23, a portion of the second main surface 112 of the capacitor in contactwith an embedding resin 9 is shown.

When measuring the thickness of a dielectric layer and that of aconductive layer of a capacitor, the following method is used. In anenlarged image of a cross section of a capacitor observed with a SEM, asshown in FIG. 23, a straight line Lc extending in the stacking directionof the body of the capacitor and passing through the center of the bodyis drawn. Then, a plurality of straight lines parallel with the straightline Lc are drawn at equal pitches S. The pitch S may be set to be aboutfive to ten times as long as the thickness of a dielectric layer or thatof a conductive layer to be measured. If, for example, a dielectriclayer having a thickness of about 1 μm is measured, the pitch S is setto be about 5 μm. The number of lines drawn on one side and that on theother side of the straight line Lc are the same. That is, an odd numberof lines including the straight line Lc are drawn. In FIG. 23, anexample in which five straight lines La through Le are drawn is shown.

Then, on each of the lines La through Le, the thickness of a dielectriclayer and that of a conductive layer are measured. If, on each of thestraight lines La through Le, a conductive layer is missing anddielectric layers join each other with the conductive layertherebetween, or if an enlarged image at a portion to be measured is notclear, the thickness or the distance is measured on another straightline separated from the straight line Lc.

When measuring the thickness of a dielectric layer 12, as shown in FIG.23, the thickness D₁ on the straight line La, the thickness D₂ on thestraight line Lb, the thickness D₃ on the straight line Lc, thethickness D₄ on the straight line Ld, and the thickness D₅ on thestraight line Le are measured, and the average value thereof is set tobe the thickness of the dielectric layer 12.

When calculating the average thickness of the plurality of dielectriclayers 12 included in the inner layer portion 11 m, the thicknesses of atotal of five dielectric layers 12 constituted by the dielectric layer12 positioned substantially at the center of the inner layer portion 11m in the height direction T and two dielectric layers 12 positioned ateach of both sides of this dielectric layer 12 are measured by using theabove-described method, and the average value thereof is set to be theaverage thickness of the plurality of dielectric layers 12 included inthe inner layer portion 11 m.

If the number of stacked dielectric layers 12 is less than five, thethicknesses of all the dielectric layers 12 are measured by using theabove-described method, and the average value thereof is set to be theaverage thickness of the dielectric layers 12.

A method for measuring the width of the side gaps 12 c is as follows. AWT cross section passing through the center of the body 11 is exposed bypolishing the body 11 and is observed with an optical microscope. Then,the side gap 12 c having the largest width is measured.

A method for measuring the width W₁ of the inner layer portion 11 m isas follows. A WT cross section passing through the center of the body 11is exposed by polishing the body 11 and is observed with an opticalmicroscope. Then, the widths of the conductive layer 13 positionedclosest to the first main surface 111, the conductive layer 13positioned closest to the second main surface 112, and the conductivelayer 13 positioned closest to the center of the inner layer portion 11m in the stacking direction are measured, and the average value of thethree measured widths is calculated.

A method for measuring the height T₁ of the inner layer portion 11 m isas follows. A WT cross section passing through the center of the body 11is exposed by polishing the body 11 and is observed with an opticalmicroscope. Then, the length of a line segment passing through thecenter of the body 11 and connecting the conductive layer 13 positionedclosest to the first main surface 111 and the conductive layer 13positioned closest to the second main surface 112 with the shortestdistance is measured.

A method for measuring the height h₁ of the first outer layer portion 12b ₁ or the height h₂ of the second outer layer portion 12 b ₂ is asfollows. A WT cross section passing through the center of the body 11 isexposed by polishing the body 11 and is observed with an opticalmicroscope. Then, the height h₁ of the first outer layer portion 12 b ₁or the height h₂ of the second outer layer portion 12 b ₂ at the centerof the body 11 in the width direction W is measured.

Analysis for the composition of components contained in the firstdielectric layer 12 x or the second dielectric layer 12 y may beconducted by using inductively coupled plasma (ICP) emissionspectrometry or a WDX. If elemental analysis is conducted by using ICPemission spectrometry, a sample is formed into a powder and is dissolvedwith an acid. Then, the resulting solution is subjected to ICP emissionspectrometry, thus specifying the composition. If elemental analysis isconducted by using a WDX, a WT cross section is exposed by polishing thebody of a capacitor embedded in a resin, and then, the composition isspecified by using a WDX attached to a SEM.

The boundary region of the outer portion having a high content of Siwith the inner portion may be identified as follows. A WT cross sectionis exposed by polishing the body of a capacitor embedded in a resin, anda backscattered electron image of the exposed WT cross section iscaptured and observed by using a SEM. Alternatively, the boundary regionmay be identified by creating element mapping of the exposed WT crosssection by using a WDX attached to a SEM and by specifying a portionhaving a high content of Si.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A multilayer ceramic capacitor comprising: a bodythat includes a plurality of dielectric layers and a plurality ofconductive layers stacked on each other in a stacking direction and thatincludes first and second main surfaces opposing each other in thestacking direction, first and second end surfaces opposing each other ina length direction and connecting the first and second main surfaces,and first and second side surfaces opposing each other in a widthdirection and connecting the first and second main surfaces and thefirst and second end surfaces; and first and second outer electrodesthat are disposed on portions of a surface of the body and oppose eachother in the length direction; wherein the body includes a first outerlayer portion including a first of the plurality of dielectric layersdefining the first main surface, a second outer layer portion includinga second of the plurality of dielectric layers defining the second mainsurface, and an inner layer portion adjacent to both of the first outerlayer portion and the second outer layer portion, the inner layerportion includes a portion extending from a first outermost conductivelayer positioned closest to the first main surface among the pluralityof conductive layers through a second outermost conductive layerpositioned closest to the second main surface among the plurality ofconductive layers in the stacking direction; a dimension of the body inthe width direction is at least 20% greater than a dimension of the bodyin the stacking direction; the dimension of the body in the widthdirection is smaller than a dimension of the body in the lengthdirection; the second outer layer portion includes an outer portionincluding the second main surface and an inner portion adjacent to bothof the outer portion and the inner layer portion; each of the innerportion and the outer portion includes Si as a secondary component; amolar ratio of the Si included in the outer portion is higher than amolar ratio of the Si included in the inner portion; a dimension of thesecond outer layer portion in the stacking direction is greater than adimension of the first outer layer portion in the stacking direction; atotal dimension of the first outer layer portion and the second outerlayer portion in the stacking direction is smaller than a dimension ofthe inner layer portion in the stacking direction; a color of the secondmain surface is different from a color of the first main surface; and acomposition of a dielectric material of the plurality of dielectriclayers included in the inner layer portion is the same as a compositionof a dielectric material of the first plurality of dielectric layersincluded in the first outer layer portion.
 2. The multilayer ceramiccapacitor according to claim 1, wherein the dimension of the inner layerportion in the stacking direction is smaller than a dimension of aportion of the inner layer portion where the plurality of conductivelayers are stacked in the width direction.
 3. The multilayer ceramiccapacitor according to claim 1, wherein the body includes side gapsbetween each of the first and second side surfaces and the inner layerportion, and a maximum dimension or an average dimension of the sidegaps in the width direction is greater than about 30 μm and less thanabout 90 μm.
 4. The multilayer ceramic capacitor according to claim 1,wherein the outer portion includes a boundary region adjacent to theinner portion, and, when viewed from the width direction, the boundaryregion includes a portion that inclines toward the first main surface asthe boundary region gets closer to one of the first and second endsurfaces.
 5. The multilayer ceramic capacitor according to claim 1,wherein the dimension of the body in the width direction is greater thanabout 0.9 mm and the dimension of the body in the stacking direction issmaller than about 0.9 mm.
 6. The multilayer ceramic capacitor accordingto claim 1, wherein the dimension of the second outer layer portion inthe stacking direction is about 90 μm or greater and is equal to orsmaller than about ¼ of the dimension of the inner layer portion in thestacking direction.
 7. The multilayer ceramic capacitor according toclaim 1, wherein the body includes side gaps between each of the firstand second side surfaces and the inner layer portion, and an averagedimension of the side gaps in the width direction is greater than thedimension of the first outer layer portion in the stacking direction. 8.The multilayer ceramic capacitor according to claim 1, wherein thedimension of the first outer layer portion in the stacking direction isabout 10 μm or greater, and the dimension of the second outer layerportion in the stacking direction is about 90 μm or greater.
 9. Amultilayer ceramic capacitor mount body comprising: the multilayerceramic capacitor according to claim 1; and a substrate on which themultilayer ceramic capacitor is mounted; wherein the second main surfaceof the multilayer ceramic capacitor faces the substrate.
 10. Themultilayer ceramic capacitor mount body according to claim 9, whereinthe substrate includes two lands on a surface of the substrate, the twolands being electrically connected to the first and second outerelectrodes of the multilayer ceramic capacitor, respectively; and adimension of each of the two lands in the width direction of the body issmaller than the dimension of the body in the width direction.
 11. Themultilayer ceramic capacitor mount body according to claim 10, wherein,the width of each of the two lands in the width direction is smallerthan the dimension of the inner layer portion in the width direction.12. A multilayer ceramic capacitor comprising: a body that includes aplurality of dielectric layers and a plurality of conductive layersstacked on each other in a stacking direction and that includes firstand second main surfaces opposing each other in the stacking direction,first and second end surfaces opposing each other in a length directionand connecting the first and second main surfaces, and first and secondside surfaces opposing each other in a width direction and connectingthe first and second main surfaces and the first and second endsurfaces; and first and second outer electrodes that are disposed onportions of a surface of the body and oppose each other in the lengthdirection; wherein the body includes a first outer layer portionincluding a first of the plurality of dielectric layers defining thefirst main surface, a second outer layer portion including a second ofthe plurality of dielectric layers defining the second main surface, andan inner layer portion adjacent to both of the first outer layer portionand the second outer layer portion, the inner layer portion includes aportion extending from a first outermost conductive layer positionedclosest to the first main surface among the plurality of conductivelayers through a second outermost conductive layer positioned closest tothe second main surface among the plurality of conductive layers in thestacking direction; a dimension of the body in the width direction is atleast 20% greater than a dimension of the body in the stackingdirection; the dimension of the body in the width direction is smallerthan a dimension of the body in the length direction; the second outerlayer portion includes an outer portion including the second mainsurface and an inner portion adjacent to both of the outer portion andthe inner layer portion; each of the inner portion and the outer portionincludes Si as a secondary component; a molar ratio of the Si includedin the outer portion is higher than a molar ratio of the Si included inthe inner portion; a dimension of the second outer layer portion in thestacking direction is greater than a dimension of the first outer layerportion in the stacking direction; a total dimension of the first outerlayer portion and the second outer layer portion in the stackingdirection is smaller than a dimension of the inner layer portion in thestacking direction; a dimension of the outer portion in the stackingdirection is about 30 μm or greater; a dimension of the inner portion inthe stacking direction is about 20 μm or greater; a difference betweenthe dimension of the second outer layer portion in the stackingdirection and the dimension of the first outer layer portion in thestacking direction is about 10 μm or greater; the body includes sidegaps between each of the first and second side surfaces and the innerlayer portion; a maximum dimension or an average dimension of the sidegaps in the width direction is greater than about 30 μm and less thanabout 90 μm; the average dimension of the side gaps in the widthdirection is greater than the dimension of the first outer layer portionin the stacking direction; a color of the second main surface isdifferent from a color of the first main surface; and a composition of adielectric material of the plurality of dielectric layers included inthe inner layer portion is the same as a composition of a dielectricmaterial of the first plurality of dielectric layers included in thefirst outer layer portion.
 13. A multilayer ceramic capacitor mount bodycomprising: the multilayer ceramic capacitor according to claim 12; anda substrate on which the multilayer ceramic capacitor is mounted;wherein the second main surface of the multilayer ceramic capacitorfaces the substrate.
 14. The multilayer ceramic capacitor mount bodyaccording to claim 13, wherein the substrate includes two lands on asurface of the substrate, the two lands being electrically connected tothe first and second outer electrodes of the multilayer ceramiccapacitor, respectively; and a dimension of each of the two lands in thewidth direction of the body is smaller than the dimension of the body inthe width direction.
 15. The multilayer ceramic capacitor mount bodyaccording to claim 14, wherein, the width of each of the two lands inthe width direction is smaller than the dimension of the inner layerportion in the width direction.